1. FIELD OF THE INVENTION
The present invention generally relates to heat exchanger construction and assembly methods. More particularly, this invention relates to a baffle assembly and method for creating at least two isolated fluid circuits within a heat exchanger.
2. DESCRIPTION OF THE PRIOR ART
Baffles are used in a variety of applications to block and direct the flow of fluids and gases through tubular members, such as a manifold of a heat exchanger. Heat exchangers typically include tubes interconnected between a pair of manifolds. To optimize heat transfer efficiency, the flow of a heat transfer fluid (gas or liquid) through the tubes is often controlled by placing baffles at certain points within the manifolds, such that separate and parallel flow regions can be established within the heat exchanger by appropriately routing the fluid through its tubes.
The prior art has suggested various baffle designs and methods for installing baffles within heat exchanger manifolds. One example is to use cup-shaped baffles that are installed within the internal passage of a manifold and then brazed in place. Brazing is desirable for forming a high-strength, fluid-tight seal with a baffle, particularly if the heat exchanger has a brazed construction. However, a difficulty with this approach is that braze flux may remain trapped within the manifold, which can corrode the interior of the heat exchanger. Another example is disclosed in U.S. Pat. No. 5,052,478 to Nakajima et al., which teaches the insertion of partitioning plates through circumferential slots formed in the wall of a heat exchanger manifold. Though the slots facilitate removal of residual braze flux from the manifold, they can substantially weaken the manifold wall, reducing its capacity to withstand numerous temperature and pressure cycles. A baffle design ansallation method that does not compromise the structural integrity of a heat exchanger manifold and avoids braze flux contamination is disclosed in commonly-assigned U.S. Pat. No. 4,762,152 to Clausen, which uses a cup-shaped baffle that is installed with a tool that forces the sidewalls of the baffle radially outward as the tool is withdrawn. In so doing, the sidewall is forced against the inner surface of the manifold, thus plastically deforming the baffle and manifold to secure the baffle in place.
In addition to routing fluids through heat exchangers, baffles have been employed to create two or more isolated fluid circuits within a single heat exchanger unit. The ability to provide multiple fluid circuits with a single heat exchanger is particularly desirable where efficient use of space is important, as in the case of automotive applications. In such applications, it becomes more important that each baffle is able to form a fluidic seal capable of surviving numerous thermal and pressure cycles, especially if intermixing of the fluids can damage the components of the separate fluid circuits. However, the sealing capability of a baffle can be severely challenged if the fluid circuits operate at significantly different pressures within the heat exchanger. For example, the integration of an air conditioning condenser and oil cooler within a single heat exchanger unit is made difficult by the fact that automotive air conditioning fluids are compressed to significantly higher pressures than peak engine oil pressures. Therefore, a baffle required for this purpose must be capable of withstanding a much higher pressure on the condenser side throughout numerous thermal and pressure cycles, and failure of the baffle is likely to result in damage to the air conditioning and engine oil systems.
Accordingly, it can be seen that if isolated fluid circuits operating at significantly different pressures are desired within a single heat exchanger unit, the baffles used to create the fluid circuits must provide reliable fluid-tight seals over many thermal and pressure cycles. In view of the prior art, an improved baffle design is required that does not compromise the structural integrity of the manifold or encourage entrapment of braze flux within the manifold.